The present invention relates to a polymer having quaternary ammonium groups and a process for the production thereof. The quaternary ammonium group-containing polymer obtained according to the present invention can be utilized as permanent antistatic agents or modifiers for plastics, bactericides or fungicides, chemicals for paper making, water treating agents and the like, and is particularly useful as permanent antistatic agents or modifiers for thermoplastic resins such as polystyrene, styrene-acrylonitrile copolymer, ABS resin and polyvinyl chloride.
Quaternary ammonium group-containing polymers have hitherto been prepared by solution polymerization of monomers having a quaternary ammonium group in a suitable solvent, as disclosed in Japanese Patent Publication Kokoku No. 49-16033 and Japanese Patent Publication Kokai No. 63-54466. In many cases, the quaternary ammonium group-containing polymers are generally required to remove the polymerization solvent therefrom when these polymers are used as additives for plastics or in other uses. However, the methods for removing the solvents disclosed in these prior art are only those according to vacuum drying and reprecipitation purification The vacuum drying and reprecipitation purification are suitable for synthesis of a small amount of a specific polymer having limited composition and molecular weight, but are not industrially suitable for obtaining a series of quaternary ammonium group-containing polymers having different compositions, glass transition temperatures, molecular weights and the like.
Also, since quaternary ammonium group-containing polymers intermolecularly cause association of the quaternary ammonium groups bonded on the polymer side chain, the melt viscosity becomes high as compared with polymers that have the same composition but amino groups are not quaternized. Thus, the polymers may require to treat for a long time at high temperature. However, since the quaternary ammonium groups are generally poor in heat stability, operation under high temperature is easy to cause discoloration, decomposition or deterioration of the polymers.
On the other hand, a so-called reverse-phase suspension polymerization is known as a method for directly obtaining particles of quaternary ammonium group-containing polymers wherein an aqueous solution of monomers having a quaternary ammonium group is dispersed in a hydrophobic solvent and polymerized. The reverse-phase suspension polymerization method may be advantageous for the production of the quaternary ammonium group-containing polymers, since the polymers are obtained in the state of precipitates or dispersion and, therefore, the polymers can be separated from the polymerization mediums simply. However, in the reverse-phase suspension polymerization method, it is difficult to obtain copolymers of the quaternary ammonium group-containing monomers and hydrophobic monomers, because an aqueous solution of hydrophilic monomers is generally dispersed in a hydrophobic solvent and polymerized. Further, even in the case that no hydrophobic monomers can be copolymerized, the production method has another disadvantage that it is required to firstly subject a monomer to a quaternization reaction in a specific solvent, and then to prepare an aqueous solution of the obtained quaternized monomer.
Such copolymers containing the hydrophobic monomer are known to be obtained by a process wherein a copolymer having tertiary amino groups is firstly prepared by a solution polymerization or the like and then treated with a quaternizing agent. However, such a process has a fear of discoloration upon the removal of the solvent, as mentioned above, and is not always simple.
It is an object of the present invention to overcome the disadvantages of the prior art.
A further object of the present invention is to provide a process for producing polymers having quaternary ammonium groups according to which the polymers can be easily separated and taken out from a solvent used in the process without requiring a step such as heating.
A still further object of the present invention is to provide a process for producing the quaternary ammonium group-containing polymers which have a high content of a hydrophobic monomer in a simple manner.
Another object of the present invention is to provide a polymer having quaternary ammonium groups obtained by such a process according to the present invention.
These and other objects of the present invention will become apparent from the description hereinafter.